Vacuum-tube grid biasing means



April 13, 1926. 1.5861510- D. G. LITTLE VACUUM TUBE GRID BIASING MEANS- Filed March 1, 1922.

INVENTOR Donald G. Liff/e.

; ATTORNEY latented Apr. 1 3.1926. 1 4

UNITED STATES PATENT OFFICE.-

noNALn G. LITTLE, OF EDGEWOOD, PENNSYLVANIA, ASSIGNOR 'ro WESTINGHOUSE ELECTRIC a MANUFACTURING COMPANY, A coRronA'rIoN or PENNSYLVANIA vAcUUu-rUBE omnnm'smo MEANS.

Application flled-Iarchfl, 1922. Serial No. 540,325.

To all whom it may concern:

Be it known that I, DONALD G. LrrrLE,'a

citizen'of the. United States, and a resident of Edgewood, in the county'of Allegheny and State of Pennsylvania, have invented a sion systems employing vacuum tubes as simple,

- more fully hereinafter.

oscillation generators or as modulators.

One object of my invention is to provide eflicient and readily adjustable means, whereby the control electrode of a vacuum tube may be caused to assume desired negative potentials with respect "to its cathode. p

Another object of my invention is to provide a wireless transmission system wherein feed-back action may be obtained between an oscillator tube and a modulator tube, tending to increase the effect of the latter. I have found that, in an electrical system employing vacuum tubes as oscillators or as amplifiers, wherein grid-leak circuits are employed, the control element of one tube may be given a desired negative potential by properly connecting it to the grid-leak circuit of another tube.

1 I have further found that, if'a vacuumtube oscillation generator emplo ing a griclleak circuit and a modulator tulie having a control electrode, which is operativelyassociated with a source of modulating currents, are parallelly associated with a constant "source of direct-current energy, feed-back action tending to increase the effects of the original *modulating currents" may be obtained by coupling the control element of the modulator tube and the grid-leak circuit of the generator tube, all as will be explained With these and other objects in view,'my invention further consists in the combination and ,in the details of structure and circuig an -'claimed.and illustrated in the accompanying arrangement hereinafter described drawing, wherein I v The single figure 1s adiagrammatic view of a wireless transmission system embodying my invention.

' In the drawing, I have shown one partic- 1 ular arrangement of circuits and apparatus to which my invention is applicable, though "comprises a condenser 7 having a low impedance to currents of radio frequency and a portion of a tuning coil 8 between tap POlIltS 9 and 11. The grid-filament circuit for the tube 1 includes abiasing condenser 12 and a portion of the tuning coil 8 between tap points. 11 and 13. A high-impedance leakage path 14, which'serves as a grid leak,

is shown as connecting the grid 3 to the hot cathode 4 through a. resistor 15 and a radiofrequency choke coil 16.

A portion of the coupling coil 8 between tap points 9 and 11 may be serially included in an antenna circuit comprising, inaddition, a ground lead 17 and an antenna 18.v

A constantsource of direct-current energy 19 comprising a direct-current generator 20 and a series-connected reactor 21 has its opposite terminals 22 and 23 connected, by conductors 24 and 25, to the anode 2 andto the hot cathode 4 of the oscillator tube 1, re-' spectively. A radio-frequency choke coil 26 may be included in the conductor. 24.

A modulator tube 30, comprising an anode '27, a controlling grid 28 and a hot cathode 29, has its anode and hot cathode connected, by conductors 31 and 32, to the opposite terminals 22 and 23 of the source of energy 19. The hot cathode 29 may be energized from a source of direct-current energy 33 through a resistor 34.

A conductor 35 serves to connect the controlling grid 28 of the modulator tube to an adjustable ta point 36 on the grid-leak resistor 15, there y admitting of the grid 28 assuming a negative potential with respect to its cathode element 29. A source of diroot-current energy 37 may be included in,

v in addition,

the conductor 35, and a primary winding 41 of which is included in a circuit containing, a source of direct-current energy 42 and a current modulating means such as a microphone transmitter 43. It will be understood, however, that while I have shown a microphone modulator, a telegraph key or any other modulating apparatus suitable for transmitting signals may be employed.

In operation, when energy is supplied to the oscillator tube 1, high frequency oscillations are generated in accordance with well-known principles. With the building up of the oscillations in the system, the negative charge on the biasing condenser 12 increases to a valve determined by the resistance of the grid-leak resistor 15. When the tube is oscillating steadily, therefore, a constant current is caused to traverse the gridleak circuit 14. By connecting the controlling element 28 of the modulator tube to a point in the grid-leak circuit, as 36, it is seen thatnegative potentials may be impressed upon the controlling element 28.

When the controlling element 28 of the modulator tube 30 is caused to assume a lowernegative potential, forexample, by the presence of a signal impulse, the power drawn by the modulator tube decreases, whereas that supplied to the oscillator tube 1 increases, inasmuch as a constant amount of energy is being supplied at all times to the system. The effect of the increase in the power supplied to the oscillator tube is to increase the amplitude of the oscillations and hence the current traversing the gridleak circuit 1%. However, an increase in the intensity of the current traversing the gridleak circuit 14: causes an increase in the negative potential impressed upon the controlling grid element 28 and hence increases the original eflect upon the controlling grid 28, tending to lower its potential still further. In like manner, the effect of a ,decrease in the negative potential of the grid 28 is correspondingly amplified by a decrease in the grid-leak potential applied thereto.

In view of the foregoing, it can readily be seen that energy may be fed back from the oscillator system to the modulator system, tending to increase the original effect of the modulating currents. The amount of feedback action, however, is dependent upon the potential of the grid 28, as determined by the direct-current source of energy 37 included in the conductor 35.

One advantage of my invention is that it admits of decreases in the number of amplifier tubes associating a source of modulating currents with its modulator tube. Other ad vantages and applications of my invention will readily suggest themselves to those skilled in the art.

While I have shown only one application resume of in invention, for the purpose of describing the same and illustrating its principles of operation, it is capable of various changes and modifications without departing from the spirit thereof. I desire, therefore, that only such limitations shall be imposed there on as are indicated in the prior art or specifically indicated in the appended claims.

I claim as my invention:

1. In an electrical apparatus, a vacuumtube generator, including a grid-filament circuit and a plate-filament circuit,'said cir cuits including elements coupling them to provide regeneration, a resistor in shunt to said coupling element in the grid-filament circuit, a second vacuum tube having a grid and a filament and means deriving poten tials from said resistor and impressin the same between the grid and filament or said second vacuum tube.

2. In an electrical system, a plurality of vacuum tubes, each having a filament, a grid and a plate, a circuit connecting the grid and filament of one of said tubes, a resistor shunting substantially all of said circuit external to said tube and means connecting an adjustable point in said resistor to the grid of another of said tubes.

In an electrical system, a source of current, a work circuit and a modulating circuit, a common connection supplying said circuits in parallel from said source, said common connection including means for preventing fluctuations in the current delivered by said source, means in addition to said prallel relation for increasing the effect upon the energy in one of said circuits of a change in the amount of energy in the other circuit.

4. In an electrical system, an oscillator generator adapted to generate oscillatory currents, said generator to modulate said currents and means dependent upon the action of said generator for effecting a transfer of energy from said generator to said modulating means, whereby the effect of the latter is increased.

5. In an electrical system, an oscillator generator having plate-filament and gridfilament circuits admitting of the generation of oscillatory currents, a high-resist ance grid leak path, means for affecting the action of said generator to modulate said currents in accordance with a signal and means associating said leakage path and said modulating means, whereby the efl'ect of the latter is increased.

6. In an electrical system, an oscillation generator, a source of energy therefor, a modulating tube, a source lating currents associated with said tube, means associating said tube and said source of .energy in such manner that energy su plied to said generator may be modulated in accordance with modulating currents, and

of modushunt to said source of energy, a controlling element for said modulator tube, signalcontrolled means for affecting the potential of said controlling element, and feed-back connections associating said grid leak and said controlling element for amplifying the elfect' of the latter.

8 In a wireless transmission system, an oscillator tube, plate-filament and grid fil a- 'ment circuits therefor, gri biasing means associated with said gr dlament circuit,

Ia high-resistance leakage path in-shunt relation to grid-biasing means,a constant source of direct-current energy associated with said plate-filament circuit, means for mamtaimng l constant the energy supplied from said source, a modulator tube connected in shunt relation to said source of energy, a control; ling element for said modulator tube, signal-controlled meansfor affecting the potential. of said controlling element, and a conductor for connecting points in said leak:

age path to said controlling element.

9. In an electrical system, a constant source of direct-current energy comprising a series-connected reactor and generator, an

" oscillator tube, plate-filament and grid-filament circuits therefor, connectidns associating said source of energy and said platefilament circuit, means for maintaining constant the energysupplied from said source,

grid biasing means associated with said grid filament circuit, a high-resistance element shunted around said grid-biasing means,

a modulation tube haying anode, grid and filament elements, conductors connecting said anode and said filament to opposite te rminals of said sourceof energy, signal-com trolled means for aflectinv the potential of said grid element, a conductor connecting said grid and alpoint'in said high resistance element and a source of modulatory currents associated with saidlatter conductor. 10, An oscillatory-current signalling system including an oscillation-generator tube having a grid condenser'and 8 g d leak in shunt thereto, a modulator tube begin a controlling grid, a source of modulated e ec-' tromotive forces 'for said controlling grid,

I biasing means for said controllinggrid com- I prising connections utilizing a potential drop in said grid leak and a'radio-frequency choke in said shunt.

11. In an oscillatory current signaling system, the combination with an'oscillatortube generator system including a grid-leak, of a modulating system including a modulator tube having a controlling grid, means for operatively associating, said modulating system with said oscillation generator system insuch manner that the amplitude of the oscillations are caused to decrease when the potential upon said controlling grid becomes less negative, and vice versa.

12. In an oscillatory-current -signaling system, the combination with anoscillatortube generator system including a-grid-leak,

of a modulating system including a modu-\ 80.

' lat-or tube having a controlling grid, and

means for operatively associating said modu 'lating system'with said oscillation generator system in such manner that the amplitude of the oscillations are caused to decrease when the potential upon said controlling grid becomes less negative, and, vice versa said means comprising biasing means'for said controlling grid comprising connections -utilizing a potential'drop in said grid-leak,

, and a radio-frequency selective impedance device in circuitnwith said grid leak.

13. A modulationv system comprising a vacuum-tube generator, having a grid, 11.-

vacuuin-tube modulating device controlling the supply of'energy to saidgenerator and so afiectingthe potential of said grid, a'grid leak carrying a current dependent upon the potential of said id and means for re ing the effect of t e modulating device 1n accordance with the-current in said grid leak;

14. In a vacuum-tube system, va. pair of vacuum tubes, a controlling element in one of said tubes, :1, source of energy, means for causin the energy from said source to be apport1oned between said tubes in accordance with the potential of" the said control element, and means for efiecting changes in the potential of said control element by the energy changes -in the other tube, whereb lat-4 the amplitude of said changesis increase 15. In an electrical system, a source of current, a Work circuit and a .modulatin circuit, a common connection supplying sai circuits in parallel. from said source, said common connection including means for preventing fluctuations in the current deliveredv -by said source and means in addition to said parallel relation co trolled by chantges the energy in the w rk circuit for. a ecting' 1 the-impedance of the modulating' circuit;

have hereunto.

' In testimony whereof, I subscribedmy name this 25th"day of Februaryl922. I v, f 5 i DONALD G; LITTLE. 

